News Review From Harvard Medical School -- Study Disputes Heart Benefit for Fish Oil
Taking fish oil pills doesn't reduce the risk of heart attack, stroke or death, a new review of earlier research finds. The review combined results of 20 studies. They included nearly 69,000 people. Most had a prior heart attack, stroke or other form of heart and artery disease. In 18 studies, people were randomly divided into 2 groups. One group took pills containing omega-3 fatty acids from fish oil. The other group took placebo (fake) pills. Overall, rates of heart attack, heart-related death and sudden death were 9% to 13% lower than for people who got placebo pills. But those differences were small enough to be caused by chance. Rates of stroke and all deaths were similar in both groups. In 2 other studies, some people were urged to eat more fatty fish. One study found a benefit from this. The other did not. Experts interviewed by USA Today, HealthDay News and Reuters Health had different views of the study. Some said it showed that people need to eat fish and not take omega-3 pills. Others said pills may help people who don't already have heart disease. The Journal of the American Medical Association published the study September 12.
By Robert H. Shmerling, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
I learned from a colleague who had trained in Europe that omega-3 fatty acid supplements were a routine treatment for anyone with heart disease in many parts of Europe. I was surprised because that didn't seem to be true in the United States.
Omega-3 fatty acids seem like good candidates to be a routine part of care for preventing heart disease. That's because they have several potential benefits that could reduce the risk of a heart attack. For example, studies suggest they may:
- Thin the blood -- This could prevent blood clots and allow blood to keep flowing freely through the arteries that feed heart muscle.
- Keep the heart rhythm regular -- An unstable rhythm is a leading cause of sudden cardiac death.
- Lower blood pressure -- High blood pressure is a major factor that increases the risk of heart disease.
They also have an excellent safety record. So why do doctors give varying advice about these supplements in different parts of the world? One answer is that when studies have actually measured the effects of omega-3 fatty acids, the results have been mixed. Some have shown benefit, while others have not.
Omega-3 fatty acids are found in many fish and plants as well as supplements. To better understand whether they are actually good for heart health, a new analysis combined data from 20 prior studies. The analysis included nearly 70,000 people. Most of them had suffered a heart attack, stroke or other heart or blood vessel problem in the past.
The researchers found no benefit of omega 3 fatty acids with respect to:
- Heart attack
- Death due to heart disease
- Sudden death
- Overall rate of death
This analysis calls into question whether routine use of omega-3 fatty acids to prevent heart and artery disease makes sense. However, it leaves open the possibility that some groups might benefit more than others. It's also possible that different amounts might be more effective than those included in these studies.
Every study analyzed in this new report included at least some people who had previous heart or artery disease. It's possible that omega-3 fatty acids are more helpful for people free of these diseases.
In this new study, only fish sources of omega-3 fatty acids were analyzed. Fatty fish, such as mackerel and salmon, are particularly rich in omega-3 fatty acids. But omega-3s can also be found in certain plant-based foods. These include flax, walnuts and canola oil. If plant-based sources had been included in this new analysis, the results could have been different.
What Changes Can I Make Now?
Whether or not omega-3 fatty acids will help to prevent heart attack and related diseases, you can take other steps to reduce your risk. For example:
- Get your blood pressure checked. If it's consistently high, lower it with diet and exercise. If necessary, you also can take medicines.
- Control your blood sugar. If you have diabetes, work with your doctors to keep your blood sugar levels in a good range. This may require medicines as well as changes to your diet and regular exercise.
- Don't smoke. If you smoke now, set a date to quit. Ask your doctor for help if you are unable to quit on your own. Avoid secondhand smoke as well.
- Control your cholesterol. This means keeping your total and LDL cholesterol levels low and your HDL cholesterol level high. Choose a diet that is low in saturated and trans fats. Lose excess weight and exercise regularly. These may be enough, but many people require medicines as well.
These measures are even more important if you have a personal or family history of heart and artery disease (such as a heart attack or stroke). Your doctor also may recommend other treatments, including low-dose aspirin and a drug called a beta-blocker.
What Can I Expect Looking to the Future?
This latest analysis is disappointing. But future research could identify a role for omega-3 fatty acids. For example, future studies could find that omega-3s in what you eat are more helpful than supplements. Or maybe omega-3 fatty acids from plant-based sources are more helpful than those from fish.
In the meantime, this new research may dampen doctors' enthusiasm for recommending omega-3 fatty acids to keep your heart healthy. Guidelines could also change. For example, the American Heart Association could drop its current advice that people eat at least 2 servings of fatty fish each week.
Then again, since you don't need a prescription to take omega-3 supplements, it's possible that this new study will have little impact on their popularity.